Known welding methods employ technologies based on a heated mirror, the melting of a thickness of material is caused by bringing a metal element raised to a high temperature into contact with the joint area of the various components; this solution has the major drawback of requiring, on the part of the user, frequent cleaning of the heating surfaces; the reason for this is that residues of material agglutinate on the edges, creating, on the one hand, an insulating additional thickness deleterious to heat transfer and, on the other hand, a skin of softened material which generates a non-homogeneous weld bead.
Methods of heating without contact are also known, employed in installations such as, especially, systems using the blowing of hot air through a nozzle; nevertheless, this method of heating requires conducting the heater as close as possible to the joint area, which involves very difficult slow movements to be reproduced by the manipulator apparatus, hence poor control of the thickness of the softened bead.
For laboratory applications, methods of heating without contact, using infrared radiation, also predominate, but this heating beam is guided according to a sweeping movement in a straight line with respect to the surfaces, and, when the component has complex profiles, a plurality of sources are used which have the tendency to radiate over the entire component rather than simply focusing the heating beam onto the joint line or the joint plane.
All the previous solutions cannot be transferred for components which have tortuous profiles, such as, especially, indented, skewed or embossed profiles, and which are mass produced, and therefore involve very short machine times and as short as possible a maintenance of the production apparatus. In addition, since the components to be joined together generally have narrow junction lines, the existing methods of heating by infrared lamp involve numerous deformations in the proximity of the joints, as well as build-up of heat within the hollow components because of a surface treatment.